Adjustable corona discharge electrode

ABSTRACT

An electrode assembly utilized in the electrical surface treatment of a material having a conductive belt of varying width. The belt is capable of being rotated to a predetermined position in accordance with the width of the material treated. In operation a corona discharge takes place only along that portion of the belt adjacent the material being treated.

United States Patent Pendleton et al.

ADJUSTABLE CORONA DISCHARGE ELECTRODE Inventors: Pyam Pendleton; MyronR.

Waldman, both of Warwick, RI.

Walco Systems, Inc., Providence,

Filed: Mar. 15, 1974 Appl. No.: 451,570

Related US. Application Data Continuation of Ser. No. 336,203, Feb. 27,1973, abandoned.

Assignee:

U.S. Cl. 250/325; 250/324; 317/262 A Int. Cl G03g 15/00 Field of Search250/324, 325; 317/262 A References Cited UNITED STATES PATENTS 5/1965Brandt et al. 250/324 VOLTAGE SOURCE June 17, 1975 3,291,711 12/1966Moyer 204/165 3,334,227 8/1967 Cipriani 250/324 3,348,022 11/1967Schirmer..... 3,397,136 8/1968 Balogh 3,409,537 11/1968 Cannon 3,419,48912/1968 Delaney 3,578,970 5/1971 Michand 250/325 Primary Examiner-JamesW, Lawrence Assistant ExaminerB. C. Anderson Attorney, Agent, orFirmR0bert T. Dunn 5 7] ABSTRACT An electrode assembly utilized in theelectrical surface treatment of a material having a conductive belt ofvarying width. The belt is capable of being rotated to a predeterminedposition in accordance with the width of the material treated. Inoperation a corona discharge takes place only along that portion of thebelt adjacent the material being treated.

9 Claims, 5 Drawing Figures PATENTEDJUN 17 I975 3; Y

VOLTAGE SOURCE VOLTAGE SOURCE VOLTAGE SOURCE ADJUSTABLE CORONA DISCHARGEELECTRODE This is a continuation of application Ser. No. 336,203 filedFeb. 27, 1973, now abandoned.

This invention relates generally to the electrical surface treatment ofmaterials by Corona Effect, and, more particularly, to an adjustableelectrode for use therewith.

It is common knowledge that some materials such as polyolefins, ie.,polyethylene, polypropylene, etc., do not have the chemical structure toreadily accept adhesives and inks including the newer types of tulolinks used in high speed presses. Furthermore, difficulties have beenencountered in bonding processes such as extrusion coating andlaminating processes. It has therefore been necessary to first pre-treatsuch materials. There are various methods by which this can be done, allof which alter the surface of the material processed to make it morereceptive to inks, adhesives,

coating materials or the like. The most common of suchmethods is theCorona Effect method.

In the corona treating of plastic film and other web materials, twoelectrodes are utilized and so positioned that the plasma formedtherebetween passes through the material being treated. Usually oneelectrode is in the form of a grounded metal roll covered with anysuitable dielectric material and the other electrode is in the form of ametal bar spaced axially over the roll or first electrode. The materialbeing treated is passed be tween the two electrodes making intimatecontact with the roll. There is usually an air gap of approximatelyone-eighth inch between the surface of the material on the dielectriccoated roll and the metal bar electrode.

One of the major problems with the equipment utilized in a Corona Effectmethod as set forth hereinabove is that materials of varying widths cannot be properly treated. It is desireable that during the treatment ofthe material, the active width of the metal bar electrode conforms tothe width of the material being treated. Such an arrangement avoidsdischarge from the electrode passing outside the material and causingdamage to the electrode, and further avoids the discharge from missingthe edge portions of the materials. In addition, it is sometimesnecessary to treat only a certain segment of the material, and suchtreatment is virtually impossible with the electrodes heretofore in use.

In the past, complex systems such as shown in U.S. Pat. No. 3,334,227have been utilized in adjusting the length of the active electrode.However, as is quite evident, such an arrangement is highly complex inconstruction and still fails when it becomes necessary to selectivelytreat portions of the material. It has become essential in the field todevelop an adjustable electrode which is not only inexpensive toconstruct, but also highly reliable in operation as well as beingcapable of selectively treating portions of the material.

The instant invention sets forth an adjustable electrode assembly for aCorona Discharge method which overcomes all the problems set forthhereinabove. In this invention the metal bar electrode of the past isreplaced with the adjustable electrode assembly of this invention whichmay take on any of a variety of configurations all within the scope ofthe invention.

The arrangement of an embodiment of the present invention utilizes abelt of wire mesh or sheet material cut on a bias. The shape of the beltwhen laid flat may resemble, for example, a truncated triangle. Thisbelt is fixedly secured to the surface of a non-conductive roller. Theroller with the belt thereon replaces the conventional metal barelectrode, with the material to be treated passing between the electrodeof this invention and a roll as heretofore in existence. Depending uponthe width of the material to be treated, the roller containing the beltelectrode of this invention can be rotated until the proper width of thebelt is juxtaposed the material passing therebeneath. The CoronaDischarge effect now properly takes place.

When a greater adjustability is required with the electrode assembly ofthis invention, the belt electrode may be enlarged and placed over twoparallel spaced rollers or one roller and a stationary bearing member.The width of the belt adjacent the material to be treated changes as theroller or rollers are rotated. The belt surface over the length of oneof the rollers acts as the electrode (metal bar) if the roller orbearing surface guiding it is of a dielectric material.

If it becomes further necessary to treat only a preselected portion of amaterial, the interior configuration of the belt may be selectedaccordingly so that the electrode is of any desired configuration.

It is therefore an object of this invention to provide -a CoronaDischarge electrode which is capable of being readily adjusted;

It is another object of this invention to provide a Corona Dischargeelectrode which takes on a preselected configuration;

It is a further object of this invention to provide a C0- rona Dischargeelectrode assembly which is economical to produce, highly reliable inoperation and which utilizes conventional, currently availablecomponents that lend themselves to standard mass producing manufacturingtechniques.

For a better understanding of the present invention together with otherand further objects thereof, reference is made to the followingdescription taken in conjunction with the accompanying drawings and itsscope will be pointed out in the appended claims.

FIG. 1 represents a pictorial view of one embodiment of the adjustableCorona Discharge electrode assembly of this invention;

FIG. 2 represents a front view of another embodiment of the adjustableCorona Discharge electrode assembly of this invention;

FIG. 3 represents a front view of a further embodiment of the adjustableCorona Discharge electrode assembly of this invention;

FIG. 4 represents a plan view of a modified belt utilized with theadjustable Corona Discharge electrode assembly of this invention; and

FIG. 5 represents matching shapes of the conductive belt and workpiecefor an embodiment where the belt and workpiece move together.

Reference is now made to FIG. 1 of the drawing which illustrates apreferred embodiment of the adjustable electrode assembly 10 of theinstant invention.

The apparatus for producing a Corona Effect for the treatment of theworkpiece 12 which may be a web of suitable material, is made up of anysuitable propelling means 14 which is usually in the form of a groundedmetal roll 16 covered by any suitable dielectric material 18. Theadjustable electrode assembly 10 of this invention comprises a beltelectrode 20 in the shape of a truncated triangle when laid flat or ofany other configuration of varying width. In addition, belt is made ofany suitable conductive material such as a flexible sheet of metal foilor wire mesh. In position, belt 20 fixedly encompasses roller 22 whichis made of any suitable non-conductive material as shown in FIG. 1.

Any conventional electrical source 21 is connected to belt 20 by brush22 or the like to provide sufficient electrical energy to produce acorona discharge between electrode or belt 20 and grounded roll 14. Thisdischarge is limited to the width W of belt 20 which varies as roller 22is rotated. Any suitable driving means such as a manual hand crank 24(FIG. 1), stepper motor 26 (FIG. 2) or pneumatic motor 28 (FIG. 3) maybe operably connected to roller 22 to provide movement thereof. When theappropriate width W of belt 20 is directly adjacent a web of material ofwidth w any satisfactory locking mechanism such as pin 30 in conjunctionwith apertures 32 may be utilized to fixedly secure belt 20 in position.The plasma formed between belt electrode 20 and grounded roll 14 isthereby limited by the length W of belt 20. Furthermore, the effectivesize of electrode 20 may be altered even with the Corona Effectapparatus in operation.

If it is found that belt 20 shown in FIG. 1 is of insufficient size toproduce the desireable width W for the electrode, the instant inventionmay take the form shown in FIGS. 2 and 3 of the drawing. In theembodiment shown in FIG. 2 adjustable electrode assembly 11 incorporatesa belt 40 therein made of the same material and configuration as belt 20shown in FIG. 1, but larger in size. Belt 40 is therefore secured arounda pair of rollers 42 and 44, respectively, as shown in FIG. 2 or aroller 42 and suitable stationary bearing 46 as shown in FIG. 3.Although roller 42 and bearing 46 are interchangeable, it is essentialin the embodiments shown in FIGS. 2 and 3 that the roller 44 or bearing46 adjacent web 12 and roll 14 be ofa non-conductive material. Upperroller 42 may either be made ofa conductive material as shown in FIG. 2or of a non-conductive material utilized with a suitable electricalconnector such as brush 48 as shown in FIG. 3.

In FIG. 2 a conventional stepper motor 26 drives any suitablearrangement such as belt and pulleys 50 in order to rotate beltelectrode 40. FIG. 3 illustrates a conventional pneumatic motor 28directly driving roller 42. It should be noted that all driving means24, 26 and 28 are interchangeable with one another as well as capable ofbeing substituted for by other conventional driving means. In theseembodiments, however, it is es- "sential that some stop means beutilized to fixedly secure belt electrode 20 or 40 in a desiredposition. Furthermore, in the embodiment shown in FIG. 3, it should benoted that roller 42 can be replaced with bearing 46 as long as themember adjacent roller 41 is a nonconductive material.

FIG. 4 illustrates a belt 60 similar to belts 20 and 40 which is made ofany suitable conductive material. Belt 60 can be mounted on any of theapparatus shown in FIGS. 1 to 3 and is utilized when only preselectedportions of a material are to be treated-For example, if it is desirableto treat only the perimeter of a web, a cutout portion 62 of any desiredshape is formed within belt 60. This cut-out 62 may be of the designshown in FIG. 4 but may be of any other configuration required in aspecific treating operation.

The use of embodiments of the present invention shown in FIGS. 1 to 4and described above provides for positioning the conductive beltelectrode to place a portion thereof at the width W of the belt onstationary position with respect to the grounded metal roll elec-' maybe moved in synchronism with the workpiece during the treatment, in sucha manner that the portion of the belt positioned opposite the groundedroll electrode is the same width as the portion of the workpiecetherebetween. This use is illustrated in FIG. 5 which shows arepresentative shape of belt 63 and workpiece 64 having the same shape.The motor drive 65 drives the rollers 42 and 44 in synchronism with themovement of the workpiece 64 moved between rollers 44 and 14 in thedirection of arrow 66.

Although this invention has been described with reference to variousembodiments, it will be understood to those skilled in the art that thisinvention is also capable of a variety of alternate embodiments withinthe spirit and scope of the appended claims.

What is claimed is:

1. An electrode assembly for use in the electrical surface treatment ofa material comprising,

a first elongated electrode having a longitudinal dimension,

a second electrode provided by an electrically conductive surface, saidsurface being of varying width from one end to the other of the lengththereof,

means having a longitudinal dimension for positioning a portion of saidsecond electrode surface spanning a selected width thereof injuxtaposition to a longitudinal surface of said first electrode,

said longitudinal dimension of said first electrode and saidlongitudinal dimension of said positioning means being in substantiallyparallel spaced relationship to one another to provide juxtaposedsurfaces of said first and second electrodes of length equal to saidselected width of said second electrode surface,

means for actuating said positioning means to move said second electrodesurface relative to said first electrode from one position to anotherposition in the direction of the length thereof, perpendicular to thelongitudinal dimension of said first electrode, to change said portionof the second electrode surface juxtaposed to said longitudinal surfaceof said first electrode, and

means for applying a voltage across said electrodes,

whereby upon passing a material to be treated between said juxtaposedfirst and second electrode surfaces in a direction perpendicular to saidselected width while an electrical voltage is applied between saidelectrodes, a corona discharge takes place between said second electrodeand said material.

2. An electrode assembly as in claim 1 wherein,

means are provided for fixing the position of the second electrodesurface relative to the first electrode before commencing the treatment.I

3. An electrode assembly as in claim 1 wherein,

said second electrode surface has the shape of a truncated triangle.

.4. An electrode assembly in claim 1 wherein,

said second electrode surface is in the form of a belt. 5. An electrodeassembly as in claim 4 wherein, said positioning means includes anon-conductive rotatable member upon which the belt is mounted. 6. Anelectrode assembly as in claim 4 wherein, said positioning meansincludes two elongated parallel, spaced members upon which the belt ismounted, one of said members positioning said selected portion of thesecond electrode surface in the central portion thereof.

1. An electrode assembly for use in the electrical surface treatment ofa material comprising, a first elongated electrode having a longitudinaldimension, a second electrode provided by an electrically conductivesurface, said surface being of varying width from one end to the otherof the length thereof, means having a longitudinal dimension forpositioning a portion of said second electrode surface spanning aselected width thereof in juxtaposition to a longitudinal surface ofsaid first electrode, said longitudinal dimension of said firstelectrode and said longitudinal dimension of said positioning meansbeing in substantially parallel spaced relationship to one another toprovide juxtaposed surfaces of said first and second electrodes oflength equal to said selected width of said second electrode surface,means for actuating said positioning means to move said second electrodesurface relative to said first electrode from one position to anotherposition in the direction of the length thereof, perpendicular to thelongitudinal dimension of said first electrode, to change said portionof the second electrode surface juxtaposed to said longitudinal surfaceof said first electrode, and means for applying a voltage across saidelectrodes, whereby upon passing a material to be treated between saidjuxtaposed first and second electrode surfaces in a directionperpendicular to said selected width while an electrical voltage isapplied between said electrodes, a corona discharge takes place betweensaid second electrode and said material.
 2. An electrode assembly as inclaim 1 wherein, means are provided for fixing the position of thesecond electrode surface relative to the first electrode beforecommencing the treatment.
 3. An electrode assembly as in claim 1wherein, said second electrode surface has the shape of a truncatedtriangle.
 4. An electrode assembly as in claim 1 wherein, said secondelectrode surface is in the form of a belt.
 5. An electrode assembly asin claim 4 wherein, said positioning means includes a non-conductiverotatable member upon which the belt is mounted.
 6. An electrodeassembly as in claim 4 wherein, said positioning means includes twoelongated parallel, spaced members upon which the belt is mounted, oneof said members positioning said selected portion of the secondelectrode surface in juxtaposition to the first electrode surface.
 7. Anelectrode assembly as in claim 6 wherein, said positioning means isactuated by rotating one of said members on its longitudinal axis.
 8. Anelectrode assembly as in claim 6 wherein, one of said members holds saidwidth portion of said second electrode surface juxtaposed said firstelectrode longitudinal surface and is non-conductive.
 9. An electrodeassembly as in claim 4 wherein, the belt has a cut-out of preselectedconfiguration in the central portion thereof.